Background/Purpose: KZR-616 is a selective inhibitor of the immunoproteasome, the form of proteasome found predominantly in immune cells. In nonclinical studies, KZR-616 blocks acute production of inflammatory cytokines, modulates T- and B-cell activation/differentiation in vitro, and is efficacious in murine SLE models¹. Recently, we presented initial safety and efficacy data from the first 2 cohorts of an open-label study of KZR-616 in SLE patients (pts) ². Here we describe their baseline (BL) profile and post-treatment changes in transcriptomic and phenotypic analyses of circulating immune cells and plasma biomarker levels.

Methods: Pts (N=13) received KZR-616 subcutaneously at 45 or 60 mg weekly for 13 weeks with follow-up through Week (W) 25. Disease assessments were performed at BL and W5, 9, 13, 17, 21, and 25. Biomarker samples were collected at BL and W5, 17, and 25 (~50% of pts had samples for all timepoints). Comparisons at BL were made to samples from 2 separate healthy volunteer (HV) studies. Proteasome activity was measured by enzymatic and active site binding assays³.  RNA sequencing was performed using Illumina TruSeq® with whole blood collected in PAXgene® RNA tubes and isolated peripheral blood mononuclear cells (PBMCs). Expression of immune gene modules⁴ was compared within and across pts. Cryopreserved PBMCs were analyzed by flow cytometry to profile immune cell subtypes. Plasma cytokines/proteins were quantified by electrochemiluminescent assays (Meso Scale Diagnostics) and colorimetric ELISAs.

Results: At BL, immunoproteasome enzymatic activity and subunit composition in SLE pts were not significantly different from that of HV. Whole blood gene expression, noted with treatment as early as W5, revealed a reduction in gene modules enriched for plasma cell, T-cell activation, inflammation, neutrophil, and IFNα response genes. Within individual pts, there was substantial heterogeneity in gene expression with the most marked changes in pts with greater clinical improvement. Consistent with the gene expression analyses, by flow cytometry, we detected reductions in double-negative B cells, class-switched memory B cells, plasmablasts, monocytes, and activated T cells in the 4 of 5 pts with available samples. Post-treatment, several SLE-related cytokines (eg, IL-6, BAFF, MIP-3β) were reduced in some pts and 3 chemokines (RANTES, MIP-3α, and MCP-4) were reduced in most pts ( >3 of 6)

Conclusion: KZR-616 treatment was correlated with changes in gene expression, immune cell subtypes, and circulating protein biomarkers in SLE pts. Consistent with nonclinical data, we demonstrated a reduction in inflammatory activity across T, B, and innate immune effector cells at transcriptomic, cellular, and protein levels, supporting a broad mechanism of action for this first-in-class agent. Analyses of additional cohorts are underway to further elucidate these initial findings and may inform future study patient stratification based on molecular or cellular diagnostic criteria.

References:

1. Muchamuel et al. ACR 2017; 69 (suppl 10).
2. Furie et al. EULAR 2019. Abstract #FR0196
3. Lickliter et al. ACR. 2017; 69 (suppl 10).
4. Chaussabel et. al., Immunity. 2008 29(1):150

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/profiling-of-gene-expression-immune-cell-subtypes-and-circulating-protein-biomarkers-in-systemic-lupus-erythematosus-patients-treated-with-the-selective-immunoproteasome-inhibitor-kzr-616/